Traps have long been used in plumbing. Designs typically involve a two-fold purpose. First, a configuration to prevent sewer gas back flow through a drain line and second, a readily cleanable trap for among other purposes, the collection of heavier weight items, such as rings or other small jewelry which may have accidently been lost down a sink drain.
One example of such a trap is U.S. Pat. No. 4,700,412 issued to Manuel. Manuel teaches a universal trap containing inlet and outlet conduits connecting to a bowl. The bowl utilizes a center post to assist in securing the bowl to the lid. In operation, the bowl remains completely filled with drainage liquid, and the conduits are both partially filled. A screen element having approximately the same diameter as the inside diameter of the inlet conduit is horizontally positioned across the opened top portion of the bowl and serves to prevent any material larger than the screen mesh to be discharged through the outlet conduit. The universal trap is supported by a pair of ring couplings which are both offset from the vertical centerline. Sedimentation is likely to build up particularly in the area behind the center post opposite the discharge point of the inlet conduit.